Organic semiconductor device, rf modulation circuit, and ic card

ABSTRACT

A pair of electrodes are provided to sandwich an organic semiconductor layer. A lead-out electrode is provided to each of the organic semiconductor layer and the two electrodes constituting the pair of electrodes. Consequently, there is provided an organic semiconductor device having a simple configuration.

TECHNICAL FIELD

The present invention relates to an organic semiconductor device, an RFmodulation circuit having the organic semiconductor device, and an ICcard having the organic semiconductor device.

BACKGROUND ART

In recent years, there have been widely developed electronic devicesusing organic semiconductor materials. Reports have been made ondevelopment of organic EL (Electro-Luminescence), organic TFT (Thin FilmTransistor), organic semiconductor laser, etc. as light emittingdevices. Out of these, particular attention is paid to the organic TFT,a type of organic transistors, as a technology for forming integratedcircuits on glass or plastic substrates at low cost.

With respect to the structure of the organic TFT, Japanese PatentLaid-Open Nos. 08-228034, 09-232589, 10-270712, etc. propose the deviceshaving the source/drain electrodes and the gate insulating film, and thegate electrode.

It has been pointed out that the organic semiconductor shows a smallmobility compared to Si semiconductors and cannot follow a highfrequency. In order to improve this point, attempts are made to enhancethe mobility by improving crystallinity of the organic semiconductor (C.Dimitrakopoulos et. al., Science, Vol. 283 (1999), P. 822), excessivelyshorten the gate length (J. H. Schon et. al., Nature, Vol. 413 (2001),P. 713), and the like.

However, any of these attempts necessitates complicated processes,leaving problems in the low cost strategy.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a simplyconfigured organic semiconductor.

Accordingly, the present invention provides an organic semiconductordevice comprising: a pair of electrodes opposite to each other on asubstrate and an organic semiconductor layer between the pair ofelectrodes; a first lead-out electrode connected to a first electrode ofthe pair of electrodes; a second lead-out electrode connected to asecond electrode of the pair of electrodes; and a third lead-outelectrode connected to the organic semiconductor layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional schematic diagram showing a layer configuration ofan organic semiconductor device according to an embodiment of thepresent invention;

FIG. 2 is a schematic diagram showing a process of manufacturing atransistor device according to example 1 of the present invention;

FIG. 3 is a schematic diagram showing a process of manufacturing thetransistor device according to example 1 of the present invention;

FIG. 4 is a schematic diagram showing a process of manufacturing thetransistor device according to example 1 of the present invention;

FIG. 5 is a schematic diagram showing a process of manufacturing thetransistor device according to example 1 of the present invention;

FIG. 6 is a schematic diagram showing a process of manufacturing thetransistor device according to example 1 of the present invention;

FIG. 7 is a schematic diagram showing the transistor device obtainedfrom processes of manufacturing the transistor device according toexample 1 of the present invention;

FIG. 8 is a schematic diagram showing power supply connected to thetransistor device according to example 1 of the present invention;

FIG. 9 is a graph showing current/voltage characteristics of thetransistor device according to example 1 of the present invention; and

FIG. 10 is a schematic diagram illustrating functional areas on an ICcard containing a transistor device according to example 2 of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

As an embodiment, the following describes an example of the organicsemiconductor device according to the present invention.

The organic semiconductor device according to an embodiment of thepresent invention provides a lead-out electrode independently to each ofa pair of electrodes and an organic semiconductor layer therebetween.

FIG. 1 is a sectional schematic diagram showing a layer configuration ofthe organic semiconductor device according to the embodiment of thepresent invention.

The reference numeral 1 represents a substrate, 2 a first electrode, 3an organic semiconductor layer, 4 a second electrode, 5 a protectivelayer, 6 a first lead-out electrode, 7 a third lead-out electrode, and 8a second lead-out electrode.

The first electrode 2 is provided on the substrate 1. The organicsemiconductor layer 3 is provided thereon. The second electrode 4 isprovided on the organic semiconductor layer 3. That is to say, this is alayered configuration. There are provided a pair of opposite electrodes(the first electrode 2 and the second electrode 4) and the organicsemiconductor layer 3 therebetween.

The first, second, and third lead-out electrodes 6, 8, 7 are connectedto the first electrode 2, the second electrode 4, and the organicsemiconductor layer 3, respectively.

The present embodiment can provide the organic semiconductor devicehaving the very simple configuration.

As shown in FIG. 1, the organic semiconductor device according to theembodiment allows the organic semiconductor layer 3 to be provided onpart of the first electrode 2. The organic semiconductor layer is notprovided on the other part of the first electrode 2. That is to say, thefirst electrode 2 is provided so as to protrude from the organicsemiconductor layer 3. According to this form, the first lead-outelectrode 6 can connect with the first electrode 2 at its excessportion.

As shown in FIG: 1, the organic semiconductor device according to theembodiment allows the second electrode 4 to be provided on part of theorganic semiconductor layer 3. The second electrode 4 is not provided onthe other part of the organic semiconductor layer 3. That is to say, theorganic semiconductor layer 3 is provided so as to protrude from thesecond electrode 4. According to this form, the third lead-out electrode7 can connect with the organic semiconductor layer 3 at its excessportion.

In the organic semiconductor device according to the embodiment, thesecond lead-out electrode 8 connects to the second electrode 4. In thismanner, the organic semiconductor layer 3 protrudes from the secondelectrode 4. The first electrode 2 surpasses the organic semiconductorlayer 3. The first through third lead-out electrodes 6, 7, and 8 can bealigned along a specified direction.

In the organic semiconductor device according to the embodiment, theprotective layer 5 is arranged so as to cover the first electrode 2, theorganic semiconductor layer 3, and the second electrode 4. The firstthrough third lead-out electrodes 6, 7, and 8 are arranged so as to betaken out from the same side (the same surface side in this case) of theprotective layer 5.

Though not shown, the organic semiconductor device according to theembodiment maintains the following relationship among areas in contactwith the respective layers: second electrode area<organic semiconductorlayer area<first electrode area. When the organic semiconductor deviceis viewed from the top of FIG. 1, the organic semiconductor layer 3 isarranged inside the first electrode 2. That is to say, the organicsemiconductor layer 3 is entirely surrounded by the excess part of thefirst electrode 2. Further, the second electrode 4 is arranged insidethe organic semiconductor layer 3. That is to say, the second electrode4 is entirely surrounded by the excess part of the organic semiconductorlayer 3. This configuration allows the second electrode 4 to be reliablyarranged inside the organic semiconductor layer 3. It is possible toprevent the second electrode 4 from being in direct contact with thefirst electrode 2.

The organic semiconductor device according to the embodiment may be ajunction-type transistor. The third lead-out electrode 7 in contact withthe organic semiconductor layer 3 can be a base electrode. One of thefirst and second lead-out electrodes 6 and 8 can be an emitter electrodeand the other lead-out electrode can be a collector electrode. In thiscase, it is desirable to use the first lead-out electrode 6 connected tothe wider first electrode 2 (having a larger area) as the collectorelectrode. Of course, the collector electrode can be the second lead-outelectrode 8 connected to the second electrode 4. It is possible tooptimally, easily, and accurately adjust the thickness of the sheetlikeorganic semiconductor layer 3 through the use of the depositiontechnology such as the vacuum deposition. Further, it is possible toobtain a satisfactory amplification phenomenon as the junction-typetransistor. If a rectangular wave of 500 kHz is input, it is possible torecognize an amplification phenomenon equivalent to several tens to ahundred of gains. Alternatively, it is possible to obtaincharacteristics based on a satisfactory cutoff frequency, i.e.,characteristics capable of maintaining a sufficient gain at a highfrequency.

For example, it is possible to assume a cutoff frequency ofapproximately 600 kHz. The organic semiconductor device according to theembodiment can be provided as a constituent element of the RF modulationcircuit.

The organic semiconductor device according to the embodiment may have anorganic semiconductor layer 8 composed of organic compound such aspentacene, for example. The organic compound to be used should havesatisfactory orientation and may show high crystallinity.

The organic semiconductor device according to the embodiment may provideFermi levels of the first electrode and the second electrode between theconduction band level and the valence band level.

The organic semiconductor device according to the embodiment may providedifferent Fermi levels for the first electrode and the second electrode.When a lower Fermi level is assigned to the collector electrode, forexample, more emitter current can be generated.

When the organic semiconductor device according to the embodiment usesthe organic semiconductor layer with the thickness of 100 nm or less, itis possible to generate more emitter current and increase the gain.

In the organic semiconductor device according to the embodiment, theorganic semiconductor layer may have the p-type or n-type conductioncharacteristic.

When the organic semiconductor device according to the embodiment uses ap-type organic semiconductor layer, the third lead-out electrode can bemade of any of metals Pt, Au, Ag, Pd, Ir, Ni, Te, Co, and Se, or analloy or an oxide containing any of these metals such as ITO (Zn or Snoxide).

When the organic semiconductor device according to the embodiment uses ap-type organic semiconductor layer, the first electrode and the secondelectrode may use the same or different materials. For example,available materials may be any of metals Ba, Ca, La, Li, Na, Sc, Sr, andY, or an alloy containing any of these metals, for example.

When the organic semiconductor device according to the embodiment usesan n-type organic semiconductor layer, the third lead-out electrode canbe made of any of metals Ba, Ca, La, Li, Na, Sc, Sr, and Y, or an alloycontaining any of these metals.

When the organic semiconductor device according to the embodiment usesan n-type organic semiconductor layer, the first electrode and thesecond electrode may use the same or different materials. For example,available materials may be any of metals Pt, Au, Ag, Pd, Ir, Ni, Te, Co,and Se, or an alloy containing any of these metals, for example.

In the organic semiconductor device according to the embodiment, thesubstrate is made of an insulating material such as a polyimide resin.In the organic semiconductor device according to the embodiment, thesubstrate material may or may not be flexible.

In the organic semiconductor device according to the embodiment, theprotective layer is made of an insulating material such as siliconoxide.

In the organic semiconductor device according to the embodiment, thefirst electrode and the organic semiconductor layer are directlyconnected to each other, and the organic semiconductor layer and thesecond electrode are directly connected to each other. It just needs tosubstantially make an electric connection between the first electrodeand the organic semiconductor layer. It may provide another very thinlayer between them. At least one of the first electrode and the organicsemiconductor layer may be configured to be a multilayer. The sameapplies to the relation between the organic semiconductor layer and thesecond electrode. It just needs to substantially make an electricconnection between the organic semiconductor layer and the secondelectrode. It may provide another very thin layer between them. At leastone of the organic semiconductor layer and the second electrode may beconfigured to be a multilayer.

The organic semiconductor device according to the embodiment is obtainedas follows. The first electrode is formed on the substrate (process 1).The organic semiconductor layer is formed on the first electrode(process 2). The second electrode is formed on the organic semiconductorlayer (process 3). The protective layer is formed so as to cover them(process 4). The protective layer is etched so that the lead-outelectrodes can be connected to the first electrode, the organicsemiconductor layer, and the second electrode (process 5). The lead-outelectrodes are formed in the etched positions, i.e., contact holes(process 6).

In the organic semiconductor device according to the embodiment, theorganic semiconductor layer can be obtained through not only theabove-mentioned vacuum deposition, but also printing techniques such astransfer and ink-jet techniques.

In the organic semiconductor device according to the embodiment, thefirst or second electrode may be obtained through the use of the vacuumdeposition technology such as DC sputtering.

In the organic semiconductor device according to the embodiment, theprotective layer may be obtained through the use of the vacuumdeposition technology such as the plasma CVD.

The organic semiconductor device according to the embodiment may use thedry etching technique that etches only required positions to createtrench holes by using a resist.

The organic semiconductor device according to the embodiment may use themetal mask technique to obtain the lead-out electrodes.

EXAMPLES Example 1

Example 1 of the present invention describes how to manufacture theorganic semiconductor device as the transistor device.

FIGS. 2 through 7 are sectional views of the transistor.

As shown in FIG. 2, the DC sputtering method is used to form a firstconductive layer 10 comprising lanthanum on the surface of an insulatingsubstrate 9 comprising a polyimide resin through a metal mask (notshown).

Then, as shown in FIG. 3, the vacuum deposition is used to form anorganic semiconductor layer 11 comprising pentacene through a metal mask(not shown).

At this time, the organic semiconductor layer has the thickness of 20nm. Further, as shown in FIG. 4, the DC sputtering method is used toform a second conductive layer 12 comprising lanthanum. The first andsecond conductive layers each have the thickness of approximately 200nm.

Then, as shown in FIG. 5, the plasma CVD is used to form a protectiveinsulating layer 13 comprising silicon oxide approximately 500 nm thick.After a resist is applied to the surface thereof, a photolithographyprocess is performed for exposure.

Then, dry etching is performed by using tetrafluoromethane as an etchantto form contact holes. As a result, the contact holes are created asshown in FIG. 6.

Then, through a metal mask (not shown), a collector electrode 14comprising platinum, a base electrode 15, and an emitter electrode 16are formed to obtain a transistor device as shown in FIG. 7.

A power supply is connected to the transistor device as shown in FIG. 8to fabricate an emitter ground circuit. The transistor device canprovide satisfactory transistor characteristics of approximately ahundred gains as shown in FIG. 9.

In terms of the frequency dependency of the gain, the transistor deviceis measured for a cutoff frequency at the emitter ground circuit toobtain the frequency of approximately 600 kHz.

When a rectangular wave of 500 kHz is input to the base electrode of thedevice manufactured by way of trial, a large collector current can beobtained in accordance with the base current, making it possible toobserve an amplification phenomenon of the transistor.

Example 2

While the embodiment has described the organic semiconductor device asthe transistor device, the example applies the organic semiconductordevice to an IC card.

FIG. 10 schematically shows functional areas on the surface of an ICcard 21 according to example 2.

The reference numeral 17 represents a magnetic recording area, 18 a ROMarray area, 19 a fuse array area, and 20 a data input/output terminalI/O.

When the card is issued, for example, a serial number and the like canbe written to the ROM array area 18. This area can be formed by not onlyon-demand printing, but also the inkjet technology.

The fuse array area 19 can disconnect a fuse for a specified number ofuses to intensify the security.

The magnetic recording area 17 is provided to stably maintain therecorded information.

These areas are provided on the entire surface of the IC card. Pluraltransistor devices according to the embodiment are provided to aswitching device, an amplification circuit, a shift register circuit,and the like in each area.

The transistor device according to the embodiment enables all the base,emitter, and collector electrodes to be taken out of the device from oneside. For this reason, it is possible to take out all the base, emitter,and collector electrodes as lead-out electrodes from one side withinthis surface. Accordingly, wiring connections are available on one sideof the IC card when the transistor devices are connected to each otheror the transistor device is connected to a semiconductor device inanother area.

Construction of a non-contact IC card requires a transistor thatprovides a sufficient gain in the RF band of 1 MHz or more. The organicsemiconductor device according to the embodiment can fulfil this withthe simple structure.

While there has been described the present invention with reference tothe embodiment and the examples, the present invention can provide thesimply configured organic semiconductor device.

1. An organic semiconductor device comprising: a pair of electrodes opposite to each other on a substrate and an organic semiconductor layer between said pair of electrodes; a first lead-out electrode connected to a first electrode of said pair of electrodes; a second lead-out electrode connected to a second electrode of said pair of electrodes; and a third lead-out electrode connected to said organic semiconductor layer.
 2. The organic semiconductor device according to claim 1, wherein said first electrode, said organic semiconductor layer, and said second electrode are substantially layered on said substrate in the order of said first electrode, said organic semiconductor layer, and said second electrode.
 3. The organic semiconductor device according to claim 2, wherein a surface for providing said organic semiconductor layer of said first electrode comprises a part for providing said organic semiconductor layer and an excess part where said organic semiconductor layer is not provided.
 4. The organic semiconductor device according to claim 3, wherein said excess part where said organic semiconductor layer is not provided surrounds said part for providing said organic semiconductor layer.
 5. The organic semiconductor device according to claim 2, wherein a surface for providing said second electrode of said organic semiconductor layer comprises a part for providing said second electrode and an excess part where said second electrode is not provided.
 6. The organic semiconductor device according to claim 5, wherein said excess part where said second electrode is not provided surrounds the part for providing said second electrode.
 7. The organic semiconductor device according to claim 1 further comprising an insulating member covering said first electrode, said organic semiconductor layer, and said second electrode on said substrate, wherein said first, second, and third lead-out electrodes are each taken out of a top surface of said insulating member.
 8. The organic semiconductor device according to claim 1, wherein said organic semiconductor layer has a thickness of 100 nm or less.
 9. An RF modulation circuit comprising said organic semiconductor device according to claim
 1. 10. An IC card comprising said organic semiconductor device according to claim
 1. 